The present invention relates to electronic energy meters, and more particularly, to selectively restricting the access available from outside the meter to a plurality of functions and modes of operation which are available within the meter.
Watthour meters frequently include provisions to selectively provide additional functions such as kilowatt demand metering. Such meters provide an indication of the power consumed during the highest consumption period since the last time the accumulating registers were zeroed. Zeroing of the accumulating registers is conventionally performed manually from outside the meter by a meter reader in the performance of his normal duties. One type of mechanical demand meter is disclosed in U.S. Pat. No. 3,586,974.
Demand registers continue to be an integral part of the utility billing system since billing is based not only upon total kilowatthour consumption but also upon peak demand. The utility must provide generating capacity to meet peak demands placed on the system, and it is in the interests of the utility to minimize peak demands in order to avoid adding expensive spinning reserve power generation capabilities which may only be utilized for short periods of time. That is, it is important for a utility to smooth out peak demands whenever possible. This is accomplished by charges based on the peak demand of a customer in order to encourage the customer to average, or spread out over the day, the customer's heavy periods of consumption of electric power.
Since demand registers are an integral part of the utility billing system, prevention of tampering is necessary. The need for security against tampering is complicated however, since ready accessibility must be provided to permit the meter reader to read and reset the demand accumulating registers. A number of security arrangements for actuators have been proposed and/or used in the past. See, for example, U.S. Pat. Nos. 4,188,575 and 4,205,520, both of which are assigned to the same assignee as the present invention. These type of actuators include a key-lock barrel which passes through the meter cover. When unlocked with a key, the barrel may be pressed inward or rotated to engage an actuator in the register. The key can then be rotated to perform the zeroing or resetting action, after which the actuator is disengaged, and the key is removed to restore the mechanism to its locked condition.
A further type of demand register reset actuator is disclosed in U.S. Pat. Nos. 3,844,474 and 4,602,211 which utilize an external hinged lever to actuate the barrel. The lever may be hinged into alignment with the stationary locking plate and is securely held in an non-operative position by a lock or shackle passing through aligned holes in the lever and the locking plate.
In the above arrangements, the actuator and locking mechanism is positioned on, and passes through, the transparent cover of the meter. That is, it is important that the meter reader be able to perform desired functions without removing the cover and exposing dangerous electrical potentials.
The recent availability of low-cost electronic storage and processing devices, particularly digital processors such as microprocessors, has permitted the replacement of some of the mechanical functions of a demand register with electronic functions. In such electronic meters the necessity for resetting the demand register continues to exist. In addition, the expanded capability of electronic meters allows the meter to display other supplemental or alternate information and/or functions including, for example, self check and register display. However, the meter display, which typically is a liquid crystal display is not capable of simultaneously displaying all of the data or functions which may be provided and/or displayed. Also, since it is not desirable to continuously display all of such data, there is a continuing need for some type of switching mechanism in order to call up supplemental or alternate display material only when desired. However, this capability should not interfere with the routine reading and resetting which is periodically performed by the meter reader.
Energy meter customer requirements and desires vary as to which functions should be available to the meter reader who typically does not have access to the interior of the meter, and which functions should be available only to a serviceman or repairman who has such access. Energy meters must be built to provide the external control accessibility as required or demanded by the customer. However, building a variety of custom designs as required by various customers greatly increases the cost and complexity of the manufacture of energy meters, and the stocking of meters and spare parts. In addition, customer practices and requirements change from time to time such that it is desirable to provide the capability to readily change the accessibility of certain functions or controls available to the meter reader from outside the meter.
Security requirements continue to dictate the need to prevent tampering with such more flexible demand meters. Furthermore, the ease or ability with which an authorized person, such as a meter reader, may switch display information or modes of operation also continues to be important.
It thus remains desirable to perform at least some of the resetting and switching or control functions from outside the cover, while barring or preventing certain other switching or control functions from outside the cover, and at the same time providing the flexibility to readily change those switching or control functions which can be performed from outside the cover. One mechanism for accomplishing some of the above objectives, but which does not provide the flexibility or simplicity of the present invention, is disclosed in U.S. Pat. No. 4,602,211 issued July 22, 1986 to P. F. Losapio and W. R. Germer, and assigned to the same assignee as the present invention, which patent is hereby incorporated by reference.